I opted for "mailing" the tax form as opposed to e-filing. I have the screen where I need to Download/Print form. However, now I realized that i need to fix an error. I dont know how to go back as there is no menu to go back to fix the 1040 form. I have

Are you printing from within the FILE section of your open return?  Or are you printing from the "Download/print" link at your Welcome Home page or the "Download/print" link in the 2016 Tax Timeline?

If you are in the FILE section of your return, are the main tabs visible?  i.e, can you click on something like the Personal Info tab to get out of the File section?  Or If you are in one of those other areas I mentioned, then the return is not open, and we can tell you how to reopen it.

Please tell me how to reOPEN it. I am in the Welcome page.

TurboTax make this hard and I don't know why.
Look for the menu action "Add a state" and click it. You don't have to actually add such a state return but your return will be open again.